Gorillas at a zoo in England have demonstrated a distinctly human trait while attempting to solve a puzzle: cheating.

The gorillas were presented with a wall-mounted puzzle that requires the user to guide a peanut through a series of obstacles by poking a stick through various holes. Eventually, the peanut reaches the bottom of the device and drops out.

Some gorillas, however, figured out an easier way to retrieve the nut.

"We've seen a lot of cheating behavior where they've been putting their lips up against the device and sucking the nut out, which was not how we intended the device to be used. But it just shows you that they're very flexible. They're capable of creating new solving strategies to access the food," Dr. Fay Clark from Bristol Zoo Gardens told Reuters.

"They have some fascinating problem-solving abilities that have probably not been witnessed before," she added.

In addition, the endangered western lowland gorillas, which were introduced to a prototype device earlier this year, have shown that they quite like the game. They regularly returned to play with it, even when there were no more nuts to win, scientists said.

Experts from the University of Bristol and Bristol Zoological Society developed the “Gorilla Game Lab” to encourage the gorillas' cognitive and puzzle-solving abilities. The prototype device had to be strong enough to withstand a frustrated gorilla, which can be seven times stronger than humans. It also had to be engaging enough to keep them coming back for more.

Each of the modules in the game “are removable, so we can take the modules out, redesign them and put in an additional module or change the actual structure. So it creates an endless stream of new and novel puzzles for them to solve," said Dr. Stuart Gray of the University of Bristol.

While the main aim of the project is to create a "positive psychological state of pleasure and satisfaction in the gorillas," the researchers are already setting their sights on more advanced models that would help zookeepers better understand both the mental and physical conditions of the animals.

"Things like eyesight, hearing, other cognitive functions — all of these could be measurable further on down the line," Gray said.